Viscosity coupled switch



March 25, 1941.

H. E. METCALF 2,236,411

VISCOS ITY COUPLED SWITCH Filed Nov. 50, 1938 3 Sheets-Sheet 1 JNVEN T012 HERBER r E. ME 7041. F.

T? ATVITYSRNEYS.

March 25, 1941. H. E. METCALF 2,236,411

VISCOS IIY COUPLED SWITCH Filed NOV. 30, 1938 3 Sheets-Sheet 2 INVENTOR, HERBERT E. METCALF. BY

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March 25, 1941. METCALF 2,236,411

VISCOS ITY COUPLED SWITCH Filed Nov. 30, 1938 S-Sheets-Sheet 3 INVENTOR, HERBERT E. METCALF Patented Mar. 25, 1941 UNiTEil ii'i'ATEfi PATENT OFFiCE VISCQSETY COUPLED SWITCH Application November 30, 1938, Serial No. 248,197

9 Claims.

My invention relates to a viscosity coupled switch, and more particularly to a switch which operates to indicate the direction of movement of a driving member by virtue of the viscosity of a coupling agent.

Among the objects of my invention are: To provide a switch operating by virtue of the viscosity of a material; to provide a switch indicating direction of motion, irrespective of the amount of motion; to provide a direction indicating switch free from wear due to pressure and thrust; to provide a switch, which after operation, automatically changes the condition set up by operation; to provide a switch having a time delay; to provide a switch operating in accordance with the rate of motion of a driving member; to provide a switch operating in accordance with both rate and direction of motion of a driving member; to provide a novel means and method of operating switch contacts; and to provide a simple and eflicient switch of novel character.

My invention possesses numerous other objects and features of advantage, some of which, together with the foregoing, will be set forth'in the following description of specific apparatus embodying and utilizing my novel method. It is therefor to be understod that my method is applicable to other apparatus, and that I do not n limit myself, in any way, to the apparatus of the present application, as I may adopt various other apparatus embodiments, utilizing the method, Within the scope of the appended claims.

Referring to the drawings:

Fig. 1 is a view, partly in cross-section and partly in elevation of one form of my invention, utilized as a simple direction indicating on and off switch.

Fig. 2 is a view partly in longitudinal section 40 and partly in elevation, of the modification shown in Fig. 1.

Fig. 3 is a view similar to that of Fig. 1, having the addition of means for breaking a contact once established.

Fig. 4 is a view partly in cross-section and partly in elevation of another modification of my invention, utilizing a fixed coupling between driving and driven members at one point on the rotational arc of the driving member, to ensure circuit 5() connection at that point.

Fig. 5 is a View partly in longitudinal section and partly in elevation, of aswitch having the reciprocal structure of the switch shown in Fig. 1.

Fig. 6 is a view partly in crosssection and partly in elevation, as indicated by the line 6-6 in Fig. 5, and in the direction shown by the arrows associated with the numerals B.

Fig. '7 is a view partly in cross-section and partly in elevation, as indicated by the'line 'll in Fig. 5, and in the direction shown by the arrows associated with the numerals 1.

Fig. 8' is a view partly in cross-section and partly in elevation, as indicated by the line 8-8 in Fig. 5, and in the direction shown by the arrows associated with the numerals 8.

Fig. 9 is a view partly in cross-section and partly in elevation, as indicated by the line 99 in Fig. 5, and in the direction shown by the arrows associated with the numerals 9.

Fig. 10 is a View partly in elevation and partly in section, similar to the view shown in Fig. 9, with the addition of a contact return spring, in this case shown under tension.

Fig. 11 is a view similar to that of Fig. 10, showing the contact spring contracted to change the relative position of the contacts.

Fig. 12 is a view similar to that of Fig. 11, showing coupling pins in zero throttle position.

Switches indicating direction of movement of a driving member have heretofore been utilized for various purposes, wherein the driving member, after having set up a predetermined switch condition, may continue to move in the direction setting up the condition, and wherein reversal of motion of the driving member immediately sets up a new condition which remains as long as the motion is continued in the reversed direction. Thus, such switches operate to open and close a circuit strictly in accordance with the direction of movement of the driving member and not in accordance with the position of the driving member.

Fundamentally and broadly, the switch of my invention may comprise five components: A stationary element, a movable driving element, and a pair of relatively movable switch members, there being a rigid connection between one of said switch members and one of said elements, and means for creating a viscous drag between the other of said switch members and the other of said elements, the viscous drag being, of course, sufiicient to cause relative movement of said switch members to establish a predetermined circuit condition upon movement of said driving element.

In the switch of my invention, as broadly stated above, the viscous coupling agent has a dual use. First, it must produce a drag, i. e., transmit power in accordance with the rate of application of the power, and second, it must allow free slippage after the predetermined switch conditions have been set-up, and in this respect the use of the viscous material for a coupling agent creating a drag to cause relative motion of the switch contacts, produces a result entirely different from the action of a friction clutch. At high rates of speed, and during the relative motion of the switch contacts, the viscous material acts as a solid coupling, i. e., the drag is approximately one hundred per cent, whereas at lower rates of speed some slippage, controlled or otherwise, may take place during relative movement.

After the relative movement of the contacts has ceased, slippage within the viscous material takes place easily because the viscous material actually acts as a lubricant and changes its characteristic into one of flow. A viscous material. therefore, may be defined, for the purposes of this application, as a sticky material having the characteristic of offering internal resistance to change of shape or to relative motion of parts thereof, this resistance, however, up to a certain point, being in accordance with the rate of change of shape. When, however, slippage is desired, such slippage shall take place with substantially uniform resistance.

Thus, I am able, by utilizing a viscous coupling agent in a switch, to create a drag sufficient to open and close contacts in the switch, to automatically, by the use of a relatively small auxiliary force, change circuit conditions after the driving member has ceased movement, thus providing a switch giving a time delay.

Inasmuch as a popular use for direction indicating switches is in conjunction with the throttle mechanism of an internal combustion engine driving a vehicle, I intend to describe my invention in reciprocal structures, as utilized in conjunction with that throttle mechanism. It should be distinctly understood, however, that the use herein shown and described is exemplary only, and that the switch of, my invention, with or without its various modifications and equivalents, may be utilized in many other places, as will occur to those skilled in the art, and to control a plurality of circuits, instead of one as herein shown and described.

Referring directly to Figs. 1 and 2 for a detailed description of one preferred form of simple on and off switch, a stationary element or case I is provided with an end bearing 2 in which a shaft 4 is journaled. On the outside of the case an operating arm 5 is attached to shaft 4 and is connected, in this example, to a throttle mechanism through a connecting rod 6. Inside the case I provide a driving element or disc I, firmly attached to shaft 4. Spaced from driving disc 1, and also mounted on shaft 4 but free to rotate thereon, is a driven element or contact disc 9. Contact disc 9 is held on shaft 4 by any convenient means, such as, for example, screw I and washer II.

I prefer to use a minimum spacing suificiently large to prevent accidental locking of the disc by grit particles or similar foreign substances.

Contact disc 9 carries a segmental moving contact I2 which is positioned and dimensioned to bridge a pair of stationary contacts or brushes I 4, attached to case I through insulating bushings I 5. One brush I4 may be connected through terminal It to ground, and the other brush may be connected through a similar terminal I6 to a signal device, such as a lamp I! in series with a grounded battery or similar source I9 of electric current. It will be obvious, however, that any exterior circuit which it is desired to control may be attached to terminals I6.

Stop means are provided to limit the rotation of contact disc 9. Although such stop means may take many forms, a simple means is a stationary pin 20 attached to case I and positioned in the path of two rotating pins 2| mounted on the contact disc 9, and pins 2| are so positioned with relation to stop pin 20 that at one end of the permissible arc of rotation of contact disc 9, segmental moving contact I2 will bridge brushes id, as shown in Fig. 1, whereas at the other end of the permissible arc contact I2 will move out from under at least one of brushes I4, thus breaking the circuit.

The case I may be closed by a plain cover I8 and supported by a mounting bracket l8.

In order that contact disc 9 be rotated by driven member I, I couple the two' discs with a viscous material 22, positioned between driving disc I and, contact disc 9 and contacting both discs, preferably filling the entire space between the discs, although obviously this is not a necessary feature.

The space between driving and driven discs occupied by the viscous material may be varied within wide limits, in accordance with the type of viscous material used as a coupling agent. For example, if materials of high viscosity are used this spacing may be large. If materials of relatively low viscosity are used the spacing may be small. In any event, however, the transmission of power between the driving and driven discs must not depend upon any frictional pressure directly exerted between the opposed faces of the driving and driven discs, but should depend solely on the drag exerted through the viscous material.

It will be noticed that I have shown the viscous material as being confined to the space between the two discs without the use of a retaining enclosure. This is accomplished by the use of a semi-solid viscous material such as, for example, semi-solid petroleum greases used as gear lubricants. I have found, for example, that a very satisfactory grease is the lubricant utilized in automotive gear boxes, and more particularly that type of grease utilized for lubrication of modern hypoid gears, such as used in rear axle assemblies of automobiles. Such greases do not become sufficiently liquid to run at temperatures encountered in automotive use and in positions where the switch ofmy invention would be normally utilized, and I have found that such greases are perfectly satisfactory for my use and stay in place between the discs.

Assuming, for purposes of illustration, that a semi-solid petroleum derivative grease is used as a coupling agent, the operation of the simple switch just described is; as follows: When the throttle mechanism moves to move arm in a direction indicated by the arrow on connecting rod 6, the viscous material moving with driven member I, drags disc 9 into the position shown in Fig. 1. Continued motion of the connecting rod in the same direction causes slippage within the grease, and the circuit through brushes I4 is maintained. When, however, the throttle mechanism is moved in the opposite direction, the viscous material immediately drags on disc 9 in the opposite direction and rotates the disc 9 to the opposite end of its permissible arc, thus breaking the circuit, and the grease thereafter allows continued rotation of the driving member'in the same direction with substantially constant slippage resistance.

Furthermore, this simple switch may be so adjusted, if desired, that it will not change circuit connections until the driving member attains a predetermined minimum rate of motion. For example, if brushes M are so designed and tensioned as to exert a definite frictional pressure opposing rotation of disc 9, then if driving member I is rotated very slowly, driven disc 9 will not be rotated against the friction of the brushes. If, however, the rate of motion of driving disc I be increased, the power transmitted through the viscous coupling agent will be increased and the drag will be sufiicient to move disc 9 against the friction of the brushes. Thus, the switch can be so adjusted as to operate to change condition only when the driving member exceeds a predetermined rate of motion, and when the drag does reach the necessary value disc 9 will be positively operated, and the higher the rate of motion of the driving member, the more positive will be the operation of the switch.

The use of a viscous material providing a drag to open and close contacts may be taken advantage of to provide a time delay switch, such as shown in Figs. 3 and 4. -Iere, driving member l, contact disc 9 together with its contact l2, brushes Hi, and stop pins 2! and 2!, are identical with the simple switch shown in Figs. 1 and 2. A resilient member or spring 2' 1 has been added, however, tangentially connected between case I and contact disc 9, and in these embodiments I have shown this spring as tending to rotate disc 9 into a position breaking connection between brushes l4, and holding disc 9 'in this position against the stop pins 20 and 2|.

Thus, the urge of spring 24 is opposed to the drag of the viscous material in one direction and adds the drag in the other direction.

In the position shown in Fig. 3 the spring is at full allowable contraction and maintains disc 9 in an off position. If, then, the driving member be rotated in a direction tending to rotate disc 9 into circuit closing position, the drag exerted by the viscous material must be sufficient to overcome the urge of spring 24. Consequently there will be a minimum rate of speed past which point the drag will rise sufficiently to overcome the urge of spring 2 1 and move disc 9. At rates below this minimum the spring will cause rotation against and equal to the drag, and contact will not be made. At all rates above, contact will be made.

Supposing, then, that the driving member becomes stationary after such a contact making rotation. With the switch shown in Fig. 1 the circuit would remain closed until the reverse rotation of the driving member was made. However, when the switch shown in Fig. 3 stops in contact making position, the force exerted by spring 24 is exerted against the viscous coupling material, and disc 9 slowly rotates back into circuit opening position against the stationary drag of the viscous material, and opens the circuit. I have found, for example, that at room temperature, positive opening of the circuit can take place with time intervals, if desired, after cessation of movement of the driving member, of many seconds. For example, with a switch having relative dimensions similar in scale proportions to the switches illustrated in Figs. 1 and 3, and using a semi-solid hypoid grease referred to above, a disc return time of live seconds may be obtained. With lighter greases smaller time intervals will obtain, and with heavier greases and materials of a higher viscosity, greater times can be obtained.

Thus, I have provided a switch which, when left by cessation of movement of the driving member in contact making position closing a circuit, will automatically, and without any further movement of the driving member, break that circuit. It will be obvious, of course, that if the circumstances require it, that the urge of the spring 24 can be exerted to close the circuit after opening thereof, if desired.

It should also be pointed out that after the riving member has attained the minimum rate of speed necessary to overcome the urge of spring 24 in the direction closing the contacts, that the contacts will stay closed so long as the speed remains above that minimum in spite of the urge of the spring.

A slight modification of the switch of Fig. 3 is shown in Fig. 4, the addition being a provision to ensure the fact that a circuit through the switch will always be established at zero throttle position, irrespective of the use of spring 24. This is accomplished by the use of a contact disc pin 25 in the path of a driving member pin 26, so that at zero throttle position driving membe-r pin 26 will move to pick up contact disc pin 25 and positively force disc 9 into contact making position, irrespective of the viscous drag or the urge of spring 24. Immediately the throttle is open, however, pin 26 will move away from pin 25 and free disc 9 to operate exactly as it operates in the device shown in Fig. 3.

In Fig. 5 I have shown a preferred reciprocal structure of the switch shown in Fig. 1. Here, the viscous drag is applied between the contact disc 9 and the case I, and acts to retard the disc rather than drive the disc. Driving memher I in this case is provided with two radially alined contact points 39 and SI, and a contact rush 32 is positioned on the contact disc 9 to sweep over and interconnect contacts 36 and 3| at one point in its arc of revolution. The two discs I and 9 are positively coupled by spaced driving pins 3-1 and positioned on the periphcry of driving member I in the path of a driven 96 extending from contact disc 9.

Thus, while disc 9 is positively driven by driving member 'i, there is a permissible are where relative movement'may take place between the two discs. At one end of this permissible arc brush 32 connects contacts 39 and Si. other end of this permissible arc brush 32 opens connection between contacts 30 and 3t. Contacts 3i! and 3! pass completely through driving member 7 and carry, on their opposite ends, brushes 3'! and 39 bearing on slip so and ll mounted on insulating cover 42. Slip rings 40 and 4| are connected through-the case to terminals 46, which are connected to the external circuit, as was the switch in Fig. 1.

The operation of this type of switch is simple. When driving member 1 is rotated the drag of the viscous material tends to keep contact disc 9 stationary. If stop pin 36 is not in contact with stop pin 34 or 35, relative motion of the two discs occurs to set up the proper circuit condition, and thereafter the driving member rotates contact disc 9 with the circuit in the condition set-up, the slippage in the viscous material allowing for the rotation of disc 9. When direction of rotation of the driving member is reversed, disc 9 again remains stationary until At the stop pin 36 is engaged by the opposite stop pin on member 1, thereby changing the circuit conditions, whereafter both discs will again rotate as a unit.

In Fig. I have shown spring 24 applied to the type of switch shown in Figs. 5 to 9 inclusive. In this modification spring 24 is tied at one end to the driving member 1 and at the other end to driven member 9, thus tending to keep the two discs in a permanently fixed relationship, preferably that relationship which breaks the circuit through the switch. This circuit breaking condition is shown in the quiescent state in Fig. 11. When, however, the driving member is rotated, the urge of spring 24 opposes the drag of the viscous material to cause relative motion of the two discs, and if the rate of motion of the driving member is sufficiently high the spring will be stretched and the circuit will be made through the switch, as shown in Fig. 10.

Thus, the end result of the switches shown in Figs. 1 to 4 inclusive is identical with the reciprocal structures, and if it is desired, a zero throttle on condition may be created by the use of a stop pin 26, extending this time from the casing and in the path of stop pin 25 on the contact disc, thus forcing the two discs into a predetermined relationship at zero throttle position. This is shown in Fig. 12.

While I have described my invention as applied to switches of reciprocal structures utilizing a rotary motion of the driving member, it will be clearly apparent to all those skilled in the art that the use of a viscous drag to open and close contacts in accordance with the direction of straight line motion of a driving member, is fully equivalent, and I do not wish, therefore, to be limited in any way to the precise form shown or to rotary motion alone.

I claim:

1. A switch comprising a stationary mounting element and a movable driving element, a pair of relatively movable switch members, a" rigid connection between one of said switch members and one of said elements, and a thin unrestrained film of viscous material between the other of said switch members and the other of said elements, the viscosity and density of said material being sufiicient to cause relative movement of said switch members to establish a predetermined circuit condition upon movement of said driving element and to prevent migration of said material from between said member and said element.

2. In combination, a driving member, a driven member spaced slightly from said driving memher, make and break means operated by motion of said driven member, a thin film of viscous coupling material bridging the space between said members only, and creating a drag therebetween, said viscous coupling material consist ing of a semi-solid which will remain semi-solid at temperatures below 300 F.

3. A switch comprising a driving member, a spaced driven member, a pair of contacts operated by motion of said driven member, and a dragging coupling of semi-solid grease'between said members.

4. A switch comprising a driving member, a spaced driven member, a pair of contact operated by motion of said driven member, a dragging coupling between said members of a material transmitting a drag in accordance with the rate of motion of said driving means, resilient means sufficient to overcome the transmitted drag when motion of said driving means is reduced in contact making direction below a predetermined minimum, and stop means rigidly coupling said driving member and said driven member in contact making position at a predetermined point in the path of said driving member.

5. A switch comprising a driving member, a spaced driven member, a pair of contacts operated by motion of said driven member, a dragging coupling between said members of a material transmitting a drag in accordance with the rate of motion of said driving means, resilient means sufficient to overcome the transmitted drag when'motion of said driving means is reduced in contact making direction below a predetermined minimum, and means for holding said contacts closed at one point in the path of said driving member against the urge of said resilient means when the motion of said driving means is reduced in contact making direction below the aforesaid predetermined minimum.

6. In combination, a case having a planar wall, a shaft entering said case through said wall, a switch disc free to rotate on said shaft and positioned adjacent said wall, a driven disc solidly mounted on said shaft on the other side of said switch disc, contacts mounted on said switch disc and said driven disc and arranged to be opened and closed upon a predetermined relative movement of said discs, and a thin film of semisolid viscous material between said wall and said switch disc only, to provide a torque producing said relative movement when said shaft and driven disc is rotated.

'7. Apparatus in accordance with claim 2, wherein the driving and driven members are closely adjacent planar discs with the viscous material positioned as a film filling the space between said discs.

8. Apparatus in accordance with claim 2, wherein the driving and driven members are closely adjacent planar discs with the viscous material positioned as a film filling the space between said discs, and wherein a case is provided surrounding said discs and free from viscous material.

9. In combination a rotatable driving member a rotatable driven member spaced therefrom, means restricting rotation of said driving member to a portion of a complete revolution. make and break means operated by motion of said driven member, and a semi-solid viscous material filling the space only, between said members.

HERBERT E. METCALF. 

